1. Field of the Invention:
This invention relates to a centrifugal pump having a pumping chamber defined by a casing providing one inlet and two outlets with the pumped fluid being directed through either one or the other of the outlets depending upon the direction of rotation of the pump impeller. More particularly, the present invention is directed to a pump of the above nature including a filter interposed within the pumping chamber between the inlet and one of the outlets for filtering water discharged through that one outlet, with the filter being cleaned by a flushing action when the impeller is reversed to pump the water through the other outlet.
2. Description of the Prior Art:
In that the pump of the present invention is primarily utilized in the environment of laundry apparatus, such as an automatic washing machine, the prior art associated with this environment will be discussed.
It is well known to continuously circulate the wash water during the agitation or wash portion of the timed cycle of an automatic washing machine to provide an opportunity to pass the wash fluid through a filtering mechanism to trap the suspended lint particles and the like which, if not filtered, tend to be caught in the clothes being laundered as the wash water flows through them. One such apparatus for filtering the circulating water is shown in U.S. Pat. No. 2,555,725 which shows a pump attached to the water-containing tub of the washing machine. The pump includes two outlets with valve means and associated valve control means to determine the flow path the pumped fluid has between a recirculating line (the line through which the water is continuously circulated) or a drain line. Interposed between the pump and the valve in the circulating line is a self-cleaning filtering mechanism which is placed in a filtering position in this line by automatic control means. Through the use of this pump and associated filter structure, as the wash fluid is being pumped through the recirculating line, the control means maintains the filter in the path of the fluid; however, when the timer control has advanced through the wash portion of the cycle to a drain and pump-out portion, the filtering means will automatically move to another position whereupon it is subjected to a flushing action by the draining fluid and thereby cleaned.
As the laundry appliance field is highly competitive the above-described pump and filtering mechanism requiring valves and automatic actuating mechanisms including solenoids, was prohibitively expensive and therefore the most prevalent type of pumping and filtering means comprises a reversible centrifugal pump which pumps to either a recirculating line or a drain line depending upon the direction of rotation of the impeller, with the recirculating line discharging above the normal water level in the clothes containing tub so that a manually accessible filter could be interposed between the recirculating line and the water. This structure eliminated the expensive valve and valve control means and also permitted the structure defining the filtering mechanism to serve as a receptacle for washing additives which were then added to the wash water by the action of the recirculating water as it passed through the filtering structure.
The above arrangement was generally accepted even though it had obvious shortcomings, not the least of which was that the water falling from the recirculating discharge tended to splash on the filtering pan and carry with it lint particles previously trapped by the filter. Further, the filter required attention in that it had to be regularly manually cleaned. And, lastly, the impact of the recirculating fluid on the filtering pan tended to aerate the water often causing an oversudsing problem.